Wireless communication devices may be referred to as mobile telephones, user equipments (UE), wireless terminals, mobile terminals, mobile stations, cellular telephones, smart phones, sensors and actuators with wireless capability, laptops, tablets and phablets, i.e. a combination of a smartphone and a tablet with wireless capability, as well as wireless modems in cars etc. Wireless communication devices are enabled to communicate or operate wirelessly in a Heterogeneous wireless communication system comprising multiple networks or Heterogeneous Networks (HetNet) with access nodes or access points, such as a cellular communications network comprising Second/Third Generation (2G/3G) network, 3G Long Term Evolution (LTE) network, Worldwide interoperability for Microwave Access (WiMAX) network, Wireless Local Area Network (WLAN) or WiFi etc.
The wireless communication device in the present context may be, for example, portable, pocket-storable, hand-held, computer-comprised, vehicle-mounted mobile devices, or any machine-type device, enabled to communicate voice and/or data via an access node with another entity, such as another communication device or a server in the wireless communication system.
5G, i.e. 5th generation mobile networks or 5th generation wireless systems denotes the next major phase of mobile telecommunications standards beyond the current 4th Generation (4G)/International Mobile Telecommunications-Advanced (IMT-Advanced) standards. In a 5G wireless communication system, machine-to-machine communication or Machine-Type Communication (MTC) is one of the major research projects. In order to maintain robust control loop functions in mission and/or time-critical MTC devices, such as communication devices used for in e.g. manufacturing, process industry, automotive or medical applications, communications with higher reliability and lower latency than previously supported in legacy systems e.g. 2nd Generation (2G), 3rd Generation (3G), 4G etc., are required. Message delays over the wireless link as well as a roundtrip time between an MTC device and its destination, e.g. an application server, must be kept low. Typical requirements are, e.g. a maximum message delay of no more than 1 ms and packet error probability of no more than 1 e-9. In order to meet such requirements, strict requirements are put on the physical layer to not introduce transport block errors, since in 3G LTE and 4G each retransmission add 8 ms to the message delay. Moreover, interruption of the wireless link must be minimized.
When cellular networks are used to transmit data for high-reliability use cases, e.g. manufacturing, process industry, automotive or medical applications in mission-critical MTC as described above, the robust control loop function requires that message delays over the wireless link must be kept low, in addition to keeping the jitter at a minimum. Depending on the application, the tolerable round-trip delays may not exceed a few milliseconds and predictable timing is also of importance. However, existing wireless systems have in contrast been designed mainly with other use cases in mind, such as voice and internet access, where a latency of 50-200 ms is acceptable, which is however too long for the mission-critical MTC.
Therefore there is a need for improved methods and apparatus for low latency applications in a wireless communication network.